Signal strength has nothing to do with the age of the technology. Even an 802.11b modem would give you a strong signal, just a slow one.
Make sure the router is set to 2.4GHz, not 5GHz.
Get close to the router (a few feet) and see if the signal improves.
Is the new router i the same place as the old one was?
Are you working on different levels? A router upstairs and the phone in the basement, almost under the router?
You're going to have to do some of the diagnosis, since we're not there to do it, and it has to be done there.